Problem is I don't think there's any way to get 'blizzard' time. There's GetGameTime() which can change based on the server time in whatever shard you end up in in CRZ or dungeons. Then there's GetServerTime(), still not usefull unless your server is on the west coast. And GetTime(), which is local time, again not useful unless you're on the west coast, and even then doesn't fix whatever logic failed and ended the event 2 hours early.

Might be "too little too late" but I've changed the mod to use local clock time instead of game time. The addon uses whatever the in-game calendar API gives it and there's very little I can do about it otherwise. :/

Make sure you have the latest versions of all 3 addons and that they're enabled in the menu and in HandyNotes settings as well. If that doesn't help, another map addon might be causing a compatibility issue.